r301735 - Fix PR32831: 'this capture while instantiating generic lambda call operator specialization
Daniel Jasper via cfe-commits
cfe-commits at lists.llvm.org
Tue May 2 05:38:32 PDT 2017
I'll revert this as it makes the following snippet makes clang crash:
class SomeClass {
public:
void foo() {
auto l = [this] { auto l = [] EXCLUSIVE_LOCKS_REQUIRED(mu_) {}; };
}
Mutex mu_;
};
(e.g. this can be added to test/SemaCXX/warn-thread-safety-parsing.cpp)
>From a brief look at the backtrace, it seems like
CurLSI->Lambda->getDeclContext() fails.
On Fri, Apr 28, 2017 at 8:49 PM, Faisal Vali via cfe-commits <
cfe-commits at lists.llvm.org> wrote:
> Author: faisalv
> Date: Fri Apr 28 22:49:17 2017
> New Revision: 301735
>
> URL: http://llvm.org/viewvc/llvm-project?rev=301735&view=rev
> Log:
> Fix PR32831: 'this capture while instantiating generic lambda call
> operator specialization
>
> When computing the appropriate cv-qualifiers for the 'this' capture, we
> have to examine each enclosing lambda - but when using the
> FunctionScopeInfo stack we have to ensure that the lambda below (outer) is
> the decl-context of the closure-class of the current lambda.
>
> https://bugs.llvm.org/show_bug.cgi?id=32831
>
> Modified:
> cfe/trunk/lib/Sema/SemaExprCXX.cpp
> cfe/trunk/test/SemaCXX/cxx1z-lambda-star-this.cpp
>
> Modified: cfe/trunk/lib/Sema/SemaExprCXX.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/
> SemaExprCXX.cpp?rev=301735&r1=301734&r2=301735&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/Sema/SemaExprCXX.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaExprCXX.cpp Fri Apr 28 22:49:17 2017
> @@ -901,17 +901,35 @@ static QualType adjustCVQualifiersForCXX
> // capturing lamdbda's call operator.
> //
>
> - // The issue is that we cannot rely entirely on the FunctionScopeInfo
> stack
> - // since ScopeInfos are pushed on during parsing and treetransforming.
> But
> - // since a generic lambda's call operator can be instantiated anywhere
> (even
> - // end of the TU) we need to be able to examine its enclosing lambdas
> and so
> - // we use the DeclContext to get a hold of the closure-class and query
> it for
> - // capture information. The reason we don't just resort to always
> using the
> - // DeclContext chain is that it is only mature for lambda expressions
> - // enclosing generic lambda's call operators that are being
> instantiated.
> + // Since the FunctionScopeInfo stack is representative of the lexical
> + // nesting of the lambda expressions during initial parsing (and is the
> best
> + // place for querying information about captures about lambdas that are
> + // partially processed) and perhaps during instantiation of function
> templates
> + // that contain lambda expressions that need to be transformed BUT not
> + // necessarily during instantiation of a nested generic lambda's
> function call
> + // operator (which might even be instantiated at the end of the TU) -
> at which
> + // time the DeclContext tree is mature enough to query capture
> information
> + // reliably - we use a two pronged approach to walk through all the
> lexically
> + // enclosing lambda expressions:
> + //
> + // 1) Climb down the FunctionScopeInfo stack as long as each item
> represents
> + // a Lambda (i.e. LambdaScopeInfo) AND each LSI's 'closure-type' is
> lexically
> + // enclosed by the call-operator of the LSI below it on the stack
> (while
> + // tracking the enclosing DC for step 2 if needed). Note the topmost
> LSI on
> + // the stack represents the innermost lambda.
> + //
> + // 2) Iterate out through the DeclContext chain (if it represents a
> lambda's
> + // call operator, and therefore must be a generic lambda's call
> operator,
> + // which is the only time an inconsistency between the LSI and the
> + // DeclContext should occur) querying closure types regarding capture
> + // information.
>
> +
> + // 1) Climb down the function scope info stack.
> for (int I = FunctionScopes.size();
> - I-- && isa<LambdaScopeInfo>(FunctionScopes[I]);
> + I-- && isa<LambdaScopeInfo>(FunctionScopes[I]) &&
> + (!CurLSI || CurLSI->Lambda->getDeclContext() ==
> + cast<LambdaScopeInfo>(FunctionScopes[I])->
> CallOperator);
> CurDC = getLambdaAwareParentOfDeclContext(CurDC)) {
> CurLSI = cast<LambdaScopeInfo>(FunctionScopes[I]);
>
> @@ -927,11 +945,17 @@ static QualType adjustCVQualifiersForCXX
> return ASTCtx.getPointerType(ClassType);
> }
> }
> - // We've run out of ScopeInfos but check if CurDC is a lambda (which can
> - // happen during instantiation of generic lambdas)
> +
> + // 2) We've run out of ScopeInfos but check if CurDC is a lambda (which
> can
> + // happen during instantiation of its nested generic lambda call
> operator)
> if (isLambdaCallOperator(CurDC)) {
> - assert(CurLSI);
> - assert(isGenericLambdaCallOperatorSpecialization(CurLSI->
> CallOperator));
> + assert(CurLSI && "While computing 'this' capture-type for a generic "
> + "lambda, we must have a corresponding
> LambdaScopeInfo");
> + assert(isGenericLambdaCallOperatorSpecialization(CurLSI->CallOperator)
> &&
> + "While computing 'this' capture-type for a generic lambda,
> when we "
> + "run out of enclosing LSI's, yet the enclosing DC is a "
> + "lambda-call-operator we must be (i.e. Current LSI) in a
> generic "
> + "lambda call oeprator");
> assert(CurDC == getLambdaAwareParentOfDeclCont
> ext(CurLSI->CallOperator));
>
> auto IsThisCaptured =
>
> Modified: cfe/trunk/test/SemaCXX/cxx1z-lambda-star-this.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
> SemaCXX/cxx1z-lambda-star-this.cpp?rev=301735&r1=301734&
> r2=301735&view=diff
> ============================================================
> ==================
> --- cfe/trunk/test/SemaCXX/cxx1z-lambda-star-this.cpp (original)
> +++ cfe/trunk/test/SemaCXX/cxx1z-lambda-star-this.cpp Fri Apr 28 22:49:17
> 2017
> @@ -229,3 +229,69 @@ int main() {
>
> } //end ns test_star_this
>
> +namespace PR32831 {
> +// https://bugs.llvm.org/show_bug.cgi?id=32831
> +namespace ns1 {
> +template <typename Func> void fun_template(Func func) {
> + (void) [&]() {
> + func(0);
> + };
> +}
> +
> +class A {
> + void member_foo() {
> + (void) [this] {
> + (void) [this] {
> + fun_template(
> + [this](auto X) {
> + auto L = [this](auto Y)
> + { member_foo(); };
> + L(5);
> + }
> + );
> + fun_template(
> + [this](auto) { member_foo(); });
> +
> + };
> + };
> + }
> +};
> +} // end ns1
> +
> +namespace ns2 {
> +
> +struct B {
> + int data = 0;
> + template<class F>
> + void mem2(F f) {
> + (void) [&] (auto f) {
> + (void) [&] { f(this->data); };
> + }(f);
> + }
> +
> +};
> +
> +class A {
> + void member_foo() {
> + (void) [this] {
> + (void) [this] {
> + B{}.mem2(
> + [this](auto X) {
> + auto L = [this](auto Y)
> + { member_foo(); };
> + L(5);
> + }
> + );
> + B{}.mem2(
> + [this](auto) { member_foo(); });
> +
> + };
> + };
> + }
> +};
> +
> +
> +} // end ns2
> +
> +}
> +
>
>
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